In general, the present invention relates to novel color pixel arrays for use in CMOS imagers.
Imagers, including complimentary metal oxide semiconductor (CMOS) imagers and charge-coupled devices (CCDs), may be used in digital imaging applications to capture scenes. An imager includes an array of pixels. Each pixel in the array includes at least a photosensitive element for outputting a signal having a magnitude proportional to the intensity of incident light contacting the photosensitive element. When exposed to incident light to capture a scene, each pixel in the array outputs a signal having a magnitude corresponding to an intensity of light at one point in the scene. The signals output from each photosensitive element may be processed to form an image representing the captured scene.
In one CMOS imager design, each pixel further includes a floating diffusion region for temporarily storing a signal from the photodiode, a reset transistor for resetting the floating diffusion region and the photodiode, a select transistor for selecting a pixel for read out and a source follower transistor for reading out the level of the pixel. Using this design, each pixel produces a signal, which is read out individually on an output line at a respective collection point. Each signal is then processed to form an image.
To capture color images, the photo sensors should be able to separately detect photons of wavelengths of light associated with different colors. For example, a photo sensor may be designed to detect first, second, and third colors (e.g., red, green and blue photons). To accomplish this, each pixel in the array of pixels may be covered with a single color filter (e.g., a red, green or blue filter). The single color filters may be arranged into a pattern to form a color filter array (“CFA”) over the array of pixels such that each individual filter in the CFA is aligned with one individual pixel in the array. Accordingly, each pixel in the array may detect the single color of light corresponding to the filter aligned with it.